PCIe is the way to go. AGP is long gone now. They are still selling AGP video cards but motherboards with AGP have gone. PCI: only in very rare cases you would want to add a PCI video card to your system. If you're trying to decide whether or not to, your system is probably outdated and should be replaced anyway.

SDRAM/DDR is out. It is all DDR2/DDR3. If you have a SDRAM/DDR board, consider replacing the motherboard as well.

AMD vs Intel. Still cost issue. Intel still has the upper end of the desktop market at a premium price. Nothing new there.

Onboard video: you still need a seperate video card for decent gaming performance. Onboard video is good enough for everyday use.

ATi vs nVidia: not completely have the picture right now, ATi seem to have their act together on drivers.

Upgrading systems: as said, for AGP systems, maybe the video card. Anything before socket AM2 or LGA775: replace the system. Most likely you have IDE drives in there, that is another dying standard. The higher-end replacement CPUs for these older boards are more expensive than a regular motherboard/CPU/memory combo that will run circles around your "upgraded" system.

OEM boxes: same rules still apply.

Even though the technology mentioned in the original posting is now becoming obsolete, all the general rules about upgrading/replacing still apply.

We hate rut, but we fear change.
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About the only thing I would add is the perils of buying a retail "prebuilt" comp. It's not as bad as it used to be, where even trying to add RAM required buying pricey, brand-specific memory from the manufacturer. For the most part, everything is industry-standard now. The only exceptions tend to be oddly-shaped PSU's and, occasionally, motherboards with different from ATX standard mounting holes. They're designed to last a few years, and an upgrade or two, but really need to be replaced after four years max. Something to bear in mind when deciding to spend a bit more to build your own, or just order a Dell and call it a day.

Yeah but by the time you want to upgrade (after 2-3 years into ownership) you'll find the OEM boards are a bit more limited than you thought, the only times I see incompatibilities between boards/video cards is on OEM systems. Because they will try and save every last penny in building them. Be it the power supply that goes kaboom or the bios designed to only use the proprietary headless video adapter upgrade (both dell optiplex 7xx series!) there are always nasty surprises in there. I stopped trying upgrades on OEM boxes...

If you buy an OEM box, consider it a black box. Use it, sell it off after it's sell-by date and get a new one. They are still not meant to be tinkered with.

We hate rut, but we fear change.
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System error, strike any user to continue...